This Program Project studies several major childhood/adolescent psychiatric disorders, each with existing evidence suggestive of familial transmission. The disorders under investigation are: attention deficit disorder with and without hyperactivity; mood disorder, and childhood onset schizophrenia. The Program Project has 4 overall aims with regard to these disorders: 1) to clarify the role of genetic factors in their etiology; 2) to define the diagnostic nosology and classification in the light of family genetic data; 3) to examine certain possible pathophysiological mechanisms; and 4) to identify significant psychological and social correlates. Project 1 ("Genetic Analysis") is the center of the Program. This project utilizes data assembled by the other projects and provides mathematical, family and genetic analyses. The other 6 projects each focuses on specific disorders, and test specific within-project hypotheses of current theoretical importance. The organization of these separate projects as a Program Project insures the collaboration among the diversity of scientists and specialties necessary for the complex data collection undertaken. In addition, each project has hypotheses to test which require family genetic studies. The Core facilities of the Program Project maximize the efficiency of the research studies by providing central consolidated resources for: recruitment, diagnosis and (clinical and laboratory) assessment of subjects; establishing and maintaining data bases; and statistical data analyses. Diagnosis in the various projects will use traditional symptom clusters, diagnostic schemes such as DSM, and, in addition, assessment measures thought to more directly reflect the pathophysiology of the disorders (e.g., attentional tests). Thus, the Project framework permits simultaneous work on cross-sectional and family studies assessing the degree of symptom overlap across diagnoses along with individual studies examining the putative substrates of these diagnoses.